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This electric conversion is finally finished, it flies fast, it is not affected by side wind and is stable and easy to land. Power is more than enough for sport flight.

The landing gear was changed by a carbon fiber one, tail servos are digital and installed in the tail from the outside, and the cabin is detachable. The access to the lipo is from the cabin, and it is placed almost touching the F1.

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As many others, the Triwon is an EPO ARF plane, inexpensive and well solved in its construction. It seems to be designed as an electric trainer more than a sailplane.
My idea was to convert it into a small glider.

Wing span: 1200 mm
Area: 19,2 dm2
Total Weight: 490 g

This is what I did:

1) First I reduce the AoA from 3° to 1° adding 2mm of balsa bellow the front part of the stabilizer.

2) I cut and paste the wing tips to add 1° of wash out, rising 2mm the trailing edges.

3) The propeller was changed for a better quality one (7x3 foldable)

4) I made sturdier the tail planes adding some balsa sticks.

5) To make transportation and storage easier I made the wing detachable.

The power plant used was: a 39g 1200rpm/v motor (Turnigy 2627-1200), a 25A ESC, plus an 11,1V 850mAhr 30C lipo.

With all these modifications the Triwon is now sensible to thermal activity, can go fast and straight efficiently, and behaves as a sailplane, a little one

After a long research I decide to convert my 72Mhz Multiplex Royal EVO into a 2,4Ghz radio.

The original conversion to Multiplex M-Link needs a mayor firmware upgrade as well as a visit to the service, so it is not cost effective for me (I live in Buenos Aires).

But Hitec offers a conversion of the EVO using its new 2,4Ghz module and receivers. It was very good news because they are at a relative good price (compared with other top brands), it has a certain level of “approval” by the manufacture, and if you are technically proficient do not need to be send to the service (despite you can do it if you want).

The RF module, that can be plugged directly to a Hitec radio, has to be un-packed to plug it into the Multiplex EVO radio port. Looking at the interior of the module, you have to do it, the boards look neat and well done.

The receivers are slim and very well packed too, and have telemetry capacity already integrated. As a detail, I loved the “2,4Ghz”golden logo in the receivers (I think marketing people were working on it), as well as the target price. The BODA antenna needs a firm installation and brings some hardware to do so.

Once in the bench I tested the brown-out recover time and, in normal mode, the reboot time is extremely fast, good point! In my test, using a haft...Continue Reading

At the field we get a simply 2,4Ghz spectrum analyzer to see what was going on in the band (and get ghost apart). Not a bad idea, considering it cost less than u$s50.

But now I want to show just a product comparison, so here there are the scan results for Futaba FASST, Hitec AFHSS and JR-Spectrum DSM2.

All the readings were taken at the field (sorry, I do not have any Faraday cage near), but I think they show the designer philosophy very well. The analyzer was an Ubicuiti Airview2 with external antenna, and the radios were at 3~4m from the scanner antenna.

The taller the graph, the stronger the signal. Blue and green dots means low occupation, yellow and red dots means great occupation of the band (condition not reached in this test)

* The Futaba system uses almost all the band, but at the same time, it uses each frequency a minimum time. The graph shows then a broad blue band.

* The Hitec system use just let's say a 60% of the band to transmit, so the use of each channel is more intensive. The graph shows a green-yellow band. In the scan mode, the system find the less used part of the spectrum to deploys its signal, so the graph can be in the another extreme or even split in two parts to avoid a strong signal in the middle of the band.

* JR-Spectrum system is quite different. It uses two narrow bands to communicate, with a powerful peak in the center. The graph talks by itself. The position of the peaks in the band changes when the transmitter is turned on.

All of them seems to be friendly, but take a look, to the last graph. It is WI-FI signal taken in a Starbucks, and it is by far the stronger and potentially more harmful signal I have seen in a normal environment.

The Mercury ESC is the fusion of a couple of devices that, until today, where separated in most of the cases. Here it is the review.

It is:

A highly programmable 50A ESC with BEC
A power meter via a Bluetooth enabled phone
A data logger (logging voltage, current, RPM, throttle position and internal temperature, plus the calculation of the power and the consumption)

Unique features

Bluetooth communication with java enabled Bluetooth cell phones (great to meter on-line data in helicopters, and cars, including RPMs).
1Mb of memory
Poles counting wizard, to make easy this task
Programmable over current cut-off, great when using small motors
Free software upgrades and limited warranty are a plus too

Installations

The PC application does not need installation, it is just an executable file, and you only need to double click over it to run it. The PS application and the on-line manual are very neat and modern looking designed.

To install the USB driver, just connect the Mercury to the PC using the provided cable and let Windows take the driver previously download from the web site, guiding it to the proper folder.

As any modern ESC, the Mercury needs to be programmed. It can be easily done following the PC application, or not so easily via the radio throttle stick.

I had to solder 4mm plugs for the battery and 3mm plugs for the motor connection. The installation in the plane was the standard.

Unless you flight indoor, you have to deal with the sun, the reflex and the gray skies. In the field I go the pilots have to face east, so the mornings are particularly tough.

Here it is what I use to deal with the different light conditions.

Glasses, they all are safety glasses, so the protect me not only from the sun and UV rays, but also from eventual particles hit for example by the propeller. Two are made by MSA (Maverik model), and the brown is made by Uvex. All of them are inexpensive and very well made and woks almost as expensive branded glasses.

Gray
The gray ones are for shinning conditions, i.e. when the level of light is high. The neutral gray color does not alter the perspective and deep sensation, so you do not have to worry about this issue. A great is that they protect the whole face and not only the front part, filtering side light too. I would like to have two degrees of grays, buy currently I only have one

Yellow
But in very cloudy days or when the level of light is low as near the sunset, the gray lenses only make the situation worst. So I use the yellow goggles. They seem to add light to some color of objects, mainly filtering the blue part of the spectrum. The problem is that the deep sensation is changed, so they required a time to be comfortable with. The very light yellow ones work better than more intense colored ones.

Brown
But some days are only partially cloudy with a combination of low and high levels of light that changes...Continue Reading

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I like my Multiplex EVO 9, it has everything I need and much more, but the drawback is the autonomy of its battery. This radio takes around 200mA from 6S the battery, that added to the self-discharge characteristic of the common NiMh makes me recharge the pack often. The charge is relatively fast, if you disconnect the pack from the radio, but never as fast as a Lipo.

The EVO had originally a 1800mAHr 7,2V NiMh pack, so the replacement with 2S Lipos is direct and safe, and then I decided to try it out.

In the table we can see a comparison of the voltage in the NiMh and Lipo packs.

1) The minimum voltage will be superior in the Lipo than in the NiMh pack, therefore it will be safe during the whole discharge. Nevertheless we shouldn’t go until the pack gets completely dead.
2) The nominal voltage is very similar in both packs, so it is ok.
3) Finally, but not less important, is that that at full charged Lipo pack voltage is under the NiMh value, and it is.

So the replacement can be safely done.

My choice was the Polyquest 2S V2 PQ-2550Rx that can be fast charger, is light, inexpensive compared with the high “C” packs, and it fits perfectly inside de radio. Another good option can be the new Polyquest 2100mAhr Rx Lipo pack, but I preferred the extra mAHr.

How-to

The space available to put the lipo is just 140mm x 35mm x 20mm (but the Velcro will take 2mm from the 20 ones), so it will limit your options. I decide to use a Polyquest 2500mA pack that...Continue Reading

I already made 200 flights with my Extra 330 with not mayor surprises, so I have to say that I did not expect to have a better performance than with the A123, but the differences were clear from the take-off to the landing. I am used to do throttle management, but speed-down it during the vertical climb amazed me.

These packs are so powerful, that now the weakest point seems to be the motors that gives 9,800 RPMs @ 680W (graphic 3), so I had to change the 13” prop for a 12” keep the motor in the safe side.

Going to the figures, I measured that the difference in voltage at the end of the routine was only 1V (0.25V per cell), and the temperature was increased from 24°C to 31°C, facts that talk about a very good performance. In this not demanding application the output voltage was very flat and a bit higher than the old Lipo packs, giving some extra rpms.

Wrapping-up

For me one important aspect is to go to the field with only two packs (or one) plus a big charger; and flight as much as if I were using three or four of the old ones, and it means to save money and the simplified the logistics.

Of course the performance of the Polyquest XF 45C is clearly superior to the pass generation; that was already very good; and new motor configurations, as the AXI 5320-18, will take full advantage of the huge available power. With current motors we must keep an eye on their temperature and RPMs because the new Lipos can spoil them easily.

Continuing with its traditional black covering, the pack’s specific weight is higher than the previous ones, but in the air the difference can not be felt. The shape depends on the number of cells, but they are long. A hard plastic protection makes them more resistant to eventual scratches, the cables are big, and the labels are right.

Really fast charging

Nevertheless that the 45C discharge rate are impressive, the 5C rate for charging is practical and money saving. The strategy for charging for me passed from have several chargers and several packs, to have only one big charger and a couple of these new packs, because it takes less than 30 minutes to have it charged. So if you are thinking in a new charger, buy one with future. Take this as an example, to charge the 4S tested packs at 5C demands 250W, and to do the same with the 6S one 480W.

To test these packs I choose the new AXI 5320-18. It is the perfect match for the new 6S 45C packs because it is the hottest AXI motor in this size (495g) and it can handle easily an 18 inches propeller, giving an authority not achieved with my last motor. The ESC was a Jeti Spin 99.

The power developed near 1600W at 6000 rpm and the result was a very firm flight (graphic 1). The system showed a remarkable authority and power sensation, nevertheless the speed was moderated. The efficiency and robustness of the AXI 5320-18...Continue Reading

There are a lot of arguments about why it is useful to meter the electric power plant performance in land and during flight.

To take the most of your costly equipment without risk of stress them and based in objective and precise information is just one of them.

The current peak during vertical climbs will tell us how far we are from the maximum values, avoiding puffed packs, broken motors and burned ESCs. The consumption will give us an exactly idea of how much longer the flight can be.

Improvements due the changes in the propeller will be felt during flight, and recorder in the Wilog.

It also can complement basic chargers, metering the charge and voltage of the packs.

The Wilog

The wilog is a tinny data logger 35x25x7 @ 16g) with the distinguish characteristic of been able to communicate in real time, via Bluetooth, with your cell-phone to show instantaneous measurements.

It means to meter very safely well apart of the propeller, even with the Wilog installed inside the plane without a simple access from the exterior.

The wilog measures and records current and voltage, and calculates power and consumption. With an update period of 340 ms, the Wilog can save up to 3 hours of information.

It can meter up to 48V (12 lipos) and 60A continuous (100 A intermittent), making it valuable for most of the sport applications.

Installation

The Wilog is a plug&play device, so no programming is needed/possible. It comes without connectors,...Continue Reading

The Thermic 70 is a classic free flight model converted by me into an electric RC sailplane. It was build in balsa and has a wing span of 1750mm.

To select the power plant I had to make some decisions. What I know is that the Thermic 70 will weight no more than 600g and that it will need around 160W/kg to safely deal with the windy whether that lately we have here. Then the motor should take around 160W/Kg x 0.6Kg = 96W from the pack. So the Lipo options will lead us to:

Using a lipo 2S pack the current will be 96W / 7.4V = 13A
Using a lipo 3S pack the current will be 96W / 11.1V = 8.6A

There are two extreme options, the light one is to use a 47g motor and a 2S 1000~1200mA pack, taking 13A. It will add no more than 120g including the controller, but everything will be at the limit and the autonomy will be limited. If you enjoy a good climate without wind and good thermals, let’s go with this set-up.

The second option is to use a 57g motor and a 3S 700~1000mA pack. This set-up will add 180g (maximum) but will work efficiently, with very good autonomy, and with enough power to deal with the wind.

For the first option the power plant can be:
AXI 2208-26
Jeti Advance Plus 12A
Polyquest 2S 1200mA XQ

I choose the second options because I am used to fly powered models, I don’t want to risk the model, and it is a good compromise between autonomy, power and weight (150g total).

To select the motor, I need to pick up one in the 1100~1200 RPM/v Kv range...Continue Reading

I have to confess that since I have discovered A123 batteries I was inclined to use them, mostly because they can deliver a huge among of current and be charged at 3~4C no risking their lifespan.

But Polyquest MX packs seems to be the Lipo’s revenge. Pilots at a competitive level will be who will take the most from this new Polyquest packs.

Besides that they are rated as 40C continuous and that can be charged at 5C, their performance in the air is something unseen at least for me. With this new Lipos generation, the weak link in the chain is again the motor and the ESC, as it was before the brushless motor introduction.

To make the comparison I change the motor of my Extra 330 from a 150g to an 180g one, and re-test the performance with the 5S A123 packs.

The MX pack (14.8V, 3000mAHr, 340g) has 30% more capacity and weight 15% less than the 5S A123 packs (16.5V, 2300mA, 400g), but compared with the Polyquest XP pack, the MX is heavier.

The section of the cables is generous, and they are multi-filament. It is important for efficiency; they must support 120A.

So, I put the 4mm connectors, glued the Velcro and went to flight. The difference in performance was notorious. It has 1V more and it has very low internal resistance (only 11 mili-ohm per cell), a value very similar to the A123 cels.

It is usual for me to do throttle management, what is not so usual is to do it meanwhile the plane is climbing vertically. During the first climb, I had to pull the...Continue Reading

nick_cool

y chucu, chucu, chuuuu...

About nick_cool

Biography

Nick_cool has almost 30 year of experience in the hobby, and he has written tenths of articles for magazines such as Model Airplane News (USA), RC Model (Spain), and Pegaso (Argentine). Today he is specialized in electric flight.